1. Field of the Invention
The present invention relates to a component holding head, a component mounting apparatus using same, and a method for mounting a component, and in particular relates to technology suitable for vacuum chucking and transporting an electronic component such as an IC, and mounting it onto a glass liquid-crystal substrate or the like.
2. Description of the Background Art
Research and development of electronic equipment in recent years has been dramatic and, combined with information technology (hereinafter referred to as IT) using the Internet, a diverse spectrum of products has been made of various types. In particular, R&D with regard to semiconductor technology has advanced the trend towards compact, thin and light electronic equipment and the like, and the trend for increased mobility in communications devices with on-board computers.
In the field of home television receivers as well, advances in manufacturing technology for liquid crystal panels has resulted in partial replacement of receivers using conventional color picture tube with those using large, flat screen displays featuring precision and fineness.
FIG. 1 of the accompanying drawings is a simplified view of part of an example of the manufacturing processes for a liquid crystal display device.
As shown in FIG. 1, a large number of glass substrates 2, referred to as liquid crystal substrates, onto which TFTs (thin-film transistors) are arranged in a matrix pattern, are held within a housing shelf (magazine) 1. These glass substrates 2 are picked up one at a time by a scalar-type picking robot 3, which moves in the X and Y axes, and placed on a relay table 4. A substrate 2 placed on the relay table 4 is transported to a connection member attachment apparatus 6 by a first linear-transport type substrate transporter 5.
FIG. 2 of the accompanying drawings is an enlarged oblique view of a substrate 2. As shown in FIG. 2, electrode lead 2a are formed in a line at the terminal parts of the periphery of the substrate 2. An anisotropic conductive film (ACF, not shown in the drawing) connection member-or the like is attached by the connection member attachment apparatus 6 to the lead 2a of the substrate 2 that has been transported to the connection member attachment apparatus 6.
Returning to FIG. 1, after attachment by the connection member attachment apparatus 6 of the connection members to the lead 2a, the substrate 2 is transported by a second linear-transport type substrate transporter 7 to a component mounting apparatus 8. At the component mounting apparatus 8, electronic components such as tape carrier packages (TCPs) are positioned above the connection members, after which connection and mounting is finished by hot pressing.
FIG. 3 of the accompanying drawings is an enlarged oblique view of an electronic component 9 in FIG. 2, viewed from the bottom thereof. As shown in FIG. 3, a chip component 92 such as an IC is connected and mounted to the lower surface of a transparent film member 91 of the electronic component 9, a large number of leads 91a being connected and formed in an arrangement in which each opposes electrodes of the chip component 92 at the terminal parts of the film member 91.
Positioning marks 91b, 91b are formed as a patterned pair along the edge of the film member 91 on both outer sides of the terminal parts of the film member 91, so as to surround the lead 91a therebetween. As shown in FIG. 2, positioning marks 2b, 2b are formed at positions corresponding to the positioning marks 91b, 91b on the substrate 2 on which the electronic components 9 are mounted.
Returning to FIG. 1, in the condition in which the electronic component 9 is held by vacuum suction by a component holding head at the component mounting apparatus 8, an imaging device images the electronic component 9 positioning marks 91b and substrate 2 positioning marks 2b. Position correction is performed with respect to both of these, so as to make the amount of relative offset between the electronic component 9 positioning marks 91b and substrate 2 positioning marks 2b zero, based on the image data, as the electronic component 9 is positioned at a prescribed location on the substrate 2, hot-pressing by the component holding head with a built-in heater being used to mount the electronic component 9 to the substrate 2.
The film member 91, which is the base material of the electronic component 9, is a polyimide resin or the like, onto which the lead 91a and positioning marks 91b are formed as copper foil patterns or gilded copper foil patterns. Whereas the polyimide resin base material has a green, brown or orange coloration, the positioning marks 91b and the like, being provided as copper foil or gilded copper foil, make it possible to obtain only a small color gradation difference relative to the positioning marks 91b and the film member 91.
Because there is only a small difference in color gradation between the positioning marks 91b and the base material, if the imaging device images the positioning mark 91b using reflected light, insufficient contrast (intensity ratio) is achieved between the positioning mark 91b and the base material. For this reason, in many component mounting apparatuses the imaging device uses light that is shone onto the positioning mark from the opposite side and passed therethrough to form an image of the terminal part of the electronic component 9.
FIG. 4 is a front elevational view showing a component mounting apparatus 8, this being the type of component mounting apparatus 8 of FIG. 1 in which transmitted light is used to form an image of the terminal part of an electronic component 9. As shown in FIG. 4, in this component mounting apparatus 8, the component holding head 81, which vacuum chucks and transports the electronic component 9, is mounted to a transport arm 83, formed by an X-Y coordinate robot, via the actuating rod 82a of a cylinder 82.
A glass substrate 2 is placed on a substrate placement stage 84 below the component holding head 81, and the substrate placement stage 84 itself is configured so as to be able to move in the horizontal plane and rotationally.
After being placed on the table 85, the electronic component 9 is vacuum chucked to the component holding head 81 and transported to over the terminal part of the substrate 2, whereupon a controller 86 having a built-in microcomputer performs relative positioning control between the electronic component 9 and the substrate 2.
The imaging device 87, which forms images of the electronic component 9 and the terminal parts on the substrate 2, is disposed on and fixed over the substrate 2 and component holding head 81.
FIG. 5 is an enlarged view showing the positional relationship between the imaging device 87, the component holding head 81, and specific parts of the substrate 2. As shown in FIG. 5, the imaging device 87 transmits light emanating from an illumination fixture (light source) 88 disposed below the substrate 2. The transmitted light is used to simultaneously form images of the positioning marks 2b and 91b of the substrate 2 and electronic component 9, respectively. In the case in which the substrate 2 is formed from an opaque material, an illumination fixture 88 such as a lamp that shines light towards the substrate 2 is, for example, built into the imaging device 87, the reflected light thereof being used to obtain a picture signal of the terminal part of the substrate 2, that is, image data of the positioning mark 2b. 
The image data of each of the positioning marks 2b and 91b obtained by the imaging device 87 are supplied to the controller 86 shown in FIG. 4, and pattern recognition or the like is used to detect the relative position offset. The controller 86 performs control of the transport arm 83 and the substrate placement stage 84 and the like so that this amount of position offset is made zero. By alignment of the relative positions of the positioning marks 2b and 91b, the lead 2a and 91a are made so as to correspond and to connect to each other.
In FIG. 5, a single imaging device 87 is shown forming an image of the positioning marks 91b and 2b of one of the electronic component 9 and the substrate 2. In reality, another separate imaging device 87 is provided so as to form images of the positioning marks 91b and 2b of the other of the electronic component 9 and substrate 2, each of these image data being supplied to the controller 86 for performing positioning control.
The lead 91a of the electronic component 9 and the lead 2a of the substrate 2 are positioned so that they are brought into mutual correspondence. After this is done, the controller 86 performs movement control of the receiving stage 89 in the directions of the arrows X and Z in FIG. 4 and FIG. 5, and controls the cylinder 82 so that it lowers the component holding head 81. The positioned electronic component 9, therefore, is pressed up against the substrate 2 supported by the receiving stage 89, via a connection member, and a mounting and connection is made by heating.
FIG. 6 is a cross-sectional view showing the condition in which block-type three-dimensional component holding head 81 is vacuum-chuck holding an electronic component 9 in the configuration shown in FIG. 4 and FIG. 5. FIG. 7 is a cross-sectional view from the direction of the arrows of line VII—VII in FIG. 6. As shown in FIG. 6 and FIG. 7, a vacuum chucking hole 81a of the component holding head 81 is provided so as to open toward the vacuum chucking surface. The vacuum chucking hole 81a is connected, via a pipe 81b, to a vacuum pump (not shown in the drawing) having an electromagnetic valve. The vacuum chucking and releasing of the electronic component 9 at the vacuum chucking hole 81a are done by valve control performed by the controller 86.
As shown in FIG. 4 and FIG. 5, in order for the imaging device 87 to obtain image data of the positioning mark 91b, it is necessary to cause light from the illumination fixture 88 to be transmitted through the terminal part of the electronic component. For this reason, the component holding head 81 holds the electronic component 9 by vacuum chucking, avoiding the edges of the terminal parts of the electronic component 9 at which the positioning mark 91b is disposed.
The base material of the electronic component 9 that is vacuum chuck held by the component holding head 81 is a film member 91 made of polyimide resin or the like. Because the desire for smaller and lighter components, however, has resulted in thinner film members 91, it is easy to change its shape. As shown by the broken line in FIG. 6, downward sagging or recurvation occurs at the terminal parts of the film member 91 not vacuum chuck held by the component holding head 81. Therefore, as shown in FIG. 8, there is deformation at the imaged positioning mark 91b part and connected lead 91a, preventing the achievement of parallelness between these deformed parts and the substrate 2 to which these are to be connected.
In FIG. 5 and FIG. 6, the reference numeral 81c denotes a heater built into the component holding head 81. The positioning marks 2b and 91b are shown as rectangles in FIG. 2, FIG. 3, FIG. 5, and FIG. 7, but can alternatively be cross-shaped or have other shapes.
As described above, a component mounting apparatus had the following problems. Specifically, as shown in FIG. 4 and FIG. 5, the imaging device 87 forms an image of the terminal part of the electronic component 9 using the light passing from the illumination fixture 88 positioned on the opposite side of the electronic component 9 (downward side in the drawing), and the controller 86 performs control, based on this image data, so that the position offset is compensated.
As shown in FIG. 6 and FIG. 8, however, the block-shaped component holding head 81 vacuum chuck holds the electronic component 9 at a location on the inside thereof, so as to avoid the edge of the film member 91. For this reason, deformation occurs, such as downward sagging or recurvation of the terminal part of the electronic component 9. A position offset therefore occurs between the position on the image screen of the positioning mark 91b imaged from directly above and the position of the positioning mark 91b which should be opposite the actual positioning mark 2b of the substrate 2. If the positioning mark 91b of the electronic component 9 is imaged for the purpose of positioning when it is in the deformed condition and the electronic component 9 is mounted onto the substrate 2 based on the image data obtained in that condition, there is a risk of misalignment occurring, and not achieving a good electrical connection.
Substrates 2 seen recently have not only thinner film members 91, but also a very narrow pitch between the lead 91a. For this reason, with the need to achieve high positioning accuracy, misalignment is a major hindrance to achieving a high yield in manufacturing liquid crystal panels, and there is a desire to achieve an improvement in this situation.